The Development of the System that Analyzes Surface Cracks by the Influence Function Method

本文采用影响函数法，在工程工作站上开发了一个有效的计算系统，可以方便地计算出裂纹表面受任意分布表面应力作用的三维表面裂纹的应力强度因子K。通过对平板半椭圆表面裂纹、平板四分之一椭圆表面裂纹、圆杆半椭圆表面裂纹、空心圆柱内表面半椭圆轴向裂纹、空心圆柱周向表面裂纹、此外，为了便于计算K值和表面裂纹在复杂应力场中的扩展，将Kij数据库存入计算机磁盘，在微机上开发了疲劳裂纹扩展模拟系统。结果表明，所建立的影响函数法和模拟系统对于评估受残余应力、热应力等复杂应力作用的表面裂纹的应力强度因子K和表面裂纹的扩展是非常有用的，模拟系统对于评估裂纹构件的剩余寿命、泄漏和/或失效概率也是非常有用的。该系统给出的计算结果已被ASME和JSME的一些标准所采用。

In this study an effective evaluating system, by which the stress intensity factor, K,can be calculated easily for the 3-dimensional surface cracks subjected to arbitrarily distributed surface stresses on the cracked surface, was developed on the engineering work-station (EWS) by using the influence function method. The data base of the influence coefficients, Kij, has been obtained by a series of finite element analysis for various cracked members, such as, semi elliptical surface crack in a flat plate, quarter-elliptical surface crack in a flat plate, semi elliptical surface crack in a round bar, semi elliptical axial crack on the inner surface of hollow cylinder, circumferential surface crack in a hollow cylinder, semi elliptical surface crack in a flange type nozzle corner, and so on. Further more, in order to evaluate the K-value and the surface crack propagating in a complex stress field easily, a simulation system of fatigue crack propagation was developed on a personal computer by storing the Kij data base in the disc of the computer. It has been shown that the developed influence function method and the simulation systems are very useful to evaluate the stress intensity factor, K,and the surface crack propagating, for the surface cracks subjected to such complicated stress as residual stress, thermal stress, and it has been shown that the simulation system is useful to assess the residual life of the cracked structural components, and leak and/or failure probabilities. The results given by the system has been used in some standard of ASME and JSME.